Production of synthetic tanning material



Patented Oct. 23, 1945 PRODUCTION OF S MAT YNTHETIO TANNING ERIAL J. Seidel, Oybin near Zittau, and Helmut Weber,

Grottau, Sudetenland. Germany; vested in the- Alien Property Custodian No Drawing. Application April 8, 1941, Serial No.

387,452. In German Claims.

This invention relates to a method for the production of synthetic tanning material and to the products of said method.

It is known to use the waste liquor of sulphite cellulose which is a by-product in the production of cellulose, as an initial material for the production of tanning material.

We have now found that tanning materials of very desirable properties can be obtained by adding to the waste liquor such a quantity of acid as is required for converting the ligninesulphonic calcium contained in the waste liquor, and condensing the waste liquor together with organic compounds, containing certain atoms or atom groups which have a close ailinity to the protein of the skin, using aldehydes or ketones as condensing agents. l

Advantageously an organicor inorganic acid is added to the waste liquor which furnishes soluble calcium compounds, such as, formic acid, lactic acid,.glycol acid, hydrochloric acid. This offers the advantage that the condensation is accelerated and leather of lighter colour can be obtained.

Suitableatoms or atom groups adapted to produce tanning material together with the lignine matter of the waste liquor, arestated hereunder, viz:

1. --0H groups in aromatic and aliphatic com pounds,

2. --SH groups in aromatic and aliphatic compounds;

3. =0 groups in aromatic compounds.

4. -NH2 groups in aromatic and aliphatic compounds,

5. =00 groups in aromatic and aliphatic compounds.

Representative of substances containing such atom groups are: Monoand polyvalent phenols, cresols, and their derivatives, naphtols, oxypyridines, thiophenols, thionaphtols, quinones, urea and thiourea, as well as derivatives of said groups. 7

Moreover, it has been found that carbo hydrates, for instance, starch and the decomposition products thereof, such as, swelling starch, soluble starch and dextrine or mixtures of these decomposition products in connection with the above mentioned substances containing the specified atom groups are excellent constituents.

According to a known method solutions containing ligninesulphonic' acid with aromatic hydroxy-compounds are condensed by means of aldehydes in a strongly acid agent. The con densate, which is separated from the reaction mixture in a solid form, cannot be used as a tany March 25, 1939 ning material in this form, buthas to be freed from the acid and adjusted to a suitab1e,pH- value.

According .to the present invention, on the other hand, the wasteliquoriscondensed after the required amount of acid has been. added. After the condensation no further treatment such as acidification or alkalisation is required, but the condensate can be drawn oil? and used as a tanning material in the form in which it is obtained in the reaction mixture. The condensate are liquid products which are readily'solublein coldwater.

Awide range of -diiiferent effects can-he produced regarding the resulting leather b the use of several condensableconstituents of the above specified types which may be added successively in' a suitable temporal order. Any kind of leather ranging from stiif soleleather to the thinnest upper leather can be made by means orthetan ning materials produced after ournovel process.

The tanning materials produced in'tbis mam ner can be mixed with'any natural andwlth any known synthetic tanning materials in any desired proportion. Moreover, they may be used with admixtures of inorganic salts, for example, chromium, zinc or aluminum salts. Furthermore, we have found that a noticeable lightening of the leather can be achieved byadding to the condensate neutral or slightly acid salts of organic sulpho-acids, for instance, sulphophenate of sodium or phenol-sulphonic sodium, cresol-sulphonic sodium, or benzol-sulphonic sodium.

It will thus be understood that the waste liquor is not condensed with a condensable com und in the presence of a free organic sulpho-acid, by

means of aldehyde or ketones. In the known re action of waste liquor with organic sulpho-acids, whose condensates have to beacidulated, dark coloured products are obtained. The dark colour is attributed to an oxidation of the sugar and other substances contained in the waste liquor and tending to resinification. This propert of substances containing products formed by reaction of waste liquor with organic sulpho-acids has an undesirable effect upon the colour of the leather which is avoided according to the present invention.

Example 1 parts of waste liquor are heated with 5 parts of formic acid to a temperature of 50 to 9'0? 0., for a period of 30 minutes; 10 parts of resorcin and 10 parts of formaldehyde are admixed and acid are intensively stirred together.

the mixture is treated by means of a reflux cooler at 80 to 90 C. for a period of 3 hours. The resuiting tanning material is full soluble in water and produces a soft, full leather.

I Example 2 100 parts of waste liquor are heated with parts of lactic acid to a temperature of 50to 60 C. for a period of 30 minutes; parts of resorcin are admixed with continuous stirring. After thorough mixing parts of dextrine and 10 parts of formaldehyde are admixed, and the mixture is treated at 80 to 90 C. at a reflux cooler for 4 to 5 hours. The resulting tanning material is water-soluble and the leather obtained by tanexcellent fullness.

Example 3 100 parts of Waste liquor plus 5 parts hydrochloric acid are intensively stirred, then admixing 5 parts of thiourea. The condensation by means of 10 parts formaldehyde is efiected in an autoclave ata pressure corresponding to 110 to 120 C. and is finished after 2V2 to 3 hours. The resulting tanning material is water-soluble and produces a still sole leather.

1 Example 4 Parts Waste liq or 100 Formic acid 5 Oxypyridine 5 Formaldehyde 10 ail-e grought together and treated as under Exame .100 parts waste liquor and 5 parts of formic 10 parts cresol are stirred up and mixed until a clear solution is obtained. The mixture is then condensed with 10 parts of formaldehyde. The resulting water-soluble tanning material gives an excellent leather.

are brought together and treated in the manner set forth under Example 5.

Example 8 Parts Waste liquor 100 Glycol acid 5 Urea 5 Destrine f 10 Formaldehyde 10 are brought together and treated in the manner set forth under Example 2.

Example 9 100 parts of waste liquor are acidulated with 5 parts of glycol acid and condensed by means of a ning with this material is characterized by an reflux cooler with a mixture consisting of 10 parts of pyrogallol and 5 parts of formaldehyde at 90 to 100 C. The resulting tannng material is readily soluble in water and produces a leather similar to quebracho.

Example 10 v 100 parts waste liquor are acidulated with 5 parts of formic acid and treated as under Exampie 5. The resulting tanning material is mixed with cresolsulphonic sodium in a proportion of 4:1. The resulting tanning material furnishes a leather similar to that produced by quebrapho taming material, but having an almost white 1 colour.

Example 11 100 parts of waste liquor are heated with 5 parts of formic acid for 30 minutes to 50 to 60 C. 10 partsof cresol and 8 parts: of acetone are admixed continuous stirring and mixture is treated by means of a reflux cooler fora period of 3 hours, at to C. The tanning material produced in this manner is fully solublein water.

Example 12 Parts Waste liquor Formic acid 5 Cresol 5 Formaldehyde 3 Acetone 2.

are mixed together and treated as describedin Example 11.

Example 13 100 parts of waste liquor are heated to 60 C. 10 parts of resorcin and 5 parts of formaldehyde are admixed with continuous stirring. The mixture is treated by means of a reflux cooler for a period of 4 hours at 80 to 90 C. The resultin tanning material is watensoluble and produces a soft leather.

The waste liquor has a. strength of 30 to 40 Beaum, advantageously of 38 B., and a calcium content of about 1 percent. However, waste liquors having a diflerent calcium content, for example, up to 3 percent calcium, may alsobe used.

The formaldehyde referred to in the examples has commercial strength, i. e., about 30 to 40 percent.

The acids referred to in the examples are formic acid of 50 percent strength, lactic acid of 80 per cent strength, glycol acid of 80 percent strength and hydrochloric acid of 36 percent strength, respectively. All proportions in the examples are by weight.

The method and product of the present invention have been described in detail with reference to specific embodiments. It is to he understood, however. that the invention is not limited by such specific reference but is broader in scope and capable of other embodiments than those specifically described.

We claim:

1. In a method of pr ducing a synthetic, watersoluble tanning material, the steps which comprise heating 100 parts by weight of waste liquor of sulphite cellulose with 5 parts-of formic acid to a temperature between 50' and 60 for a period or 30 minutes, adding 10 parts resorcin and 10 parts formaldehyde. with continuous stirring. and treating the product at 80' to 90' C. by means of a reflux cooler for a period of three hours. 7

2. The product of the process of claim 3.

3. In a method of producing synthetic liquid products suitable as water soluble tanning materials, the steps which comprise adding to waste liquor of sulfite cellulose, an acid which will form soluble calcium compounds therewith, the ratio of said sulfite cellulose waste liquor to acid being 20 Y to 1, adding a compound selected from the group consisting of phenol, cresols, naphthols, oxypyridines, thiophenols and quinones, adding a carbohydrate of the group consisting of starch and dextrin and then reacting said mixture with a cornpound selected from the group consisting of aldehydes and ketones.

4. In a method of producing synthetic liquid products suitable as water soluble tanning ma terials, the steps which comprise adding to waste liquor of suliite cellulose, an acid which will form soluble calcium compounds therewith, the ratio or said sulfite cellulose waste liquor to acid being 20 to 1, adding a compound selected from the group consisting of phenol, cresols, naphthols, oxypyridines, thiophenols and quinones, adding starch and then reacting said mixture with a compound selected from the group consisting of aldehydes and ketones.

5. In a method of producing synthetic liquid products suitable as water soluble tanning materials, the steps which comprise adding to waste 

